The Armour Archive

I am thinking of ordering from a machine shop 1280 small hexagonal plates about the size of dime with four holes for Japanese 'brigandine' and ordering 1280 small rectangular plates (about 1.5x2 in) for Japanese scales for 'cuisses' (haidate). I have no prior experience with machine shop orders. I plan on submitting specifications to this 'online shop' via an AutoCAD diagram.

The material will be 1mm mild steel.

Is 0.050" chamfering of the corners going to provide a smooth enough corner for safe handling and SCA combat?

Are there any 'gotchas' I should be familiar with before making my first shop order?

Thanks for any tips or pointers you may have.

Most laser/plasma/water cnc shops I know can take DXF files which is the standard export file for autocad so you should be ok. Be sure to specify where you want the kerf (inside the line, outside the line, on the line) and try to specify at the edges of one plate can be cut simultaneously with the edges of an adjacent plate. This will reduce waste and improve your PPM rate.

Make sure any holes are at least 1 material thickness in diameter. Provide a hard copy print and be specific about tollerances, which should be loose (despite loose tolerances modern machining will be very consistant anyway). Depending on material thickness and machines some shops can cut multiple layers simultaneously... only do this with water as laser or plasma will probably stick together.

Skip the chamfer and have the cutting shop recomend a company with a tumbler. Any shop that CNC's plates that small regularly will be able to make recomendations. The recomended aggregate depends on the size of the holes.

Specify ahead of time that this is not a business order and you will be paying by credit card or cash (their preference). Some companies will refuse to do business unless you are issuing them a P.O. Let them refuse and go elsewhere. Some companies will do work under the table if you are paying cash. These are your best suppliers.

Do not expect to bring your own steel. They probably get a better price than you do anyway.

It helps if your drawings look profesional. Include a drawing title block with part number, description, revision control number, material spec and date and most importantly CONTACT INFORMATION. For you this is a hobby, for them it is business and time is money. Don't make them waste time looking for missing information.

These are just a few thoughts from working in related industries. I hope it all works out for you.

Good luck,
Sean Powell

I had a bad experience with waterjet cutting.

make sure you get a written bid.

I happen to do this sort of stuff for a living, Sean hit most of the points. I've also shopped out armour plates (for coats of plates) to a laser-cutting outfit.

You will, as Sean said, want to specify exactly what material you want, exactly what thickness, and dimensions to completely define the part. Also as Sean said, you must specify tolerances for all dimensions. Tighter dimensions equals higher cost. Ask them what their standard manufacturing tolerances are and go with that if it is acceptable.

To get the parts with no sharp edges, on all sheetmetal parts I simply put the following not:

NOTE: PART TO BE FREE OF BURRS AND SHARP EDGES.

How they achieve that is up to them (you don't care).

You should not have to specify kerf (cutting inside or outside the line) - your print provides finished dimensions for the PARTS you are buying - how they choose to cut it is their problem. They can use a chisel for all you care as long as the parts come in to print.

Get a written quote before proceding.

Steve

[quote="Ron Broberg"]Is 0.050" chamfering of the corners going to provide a smooth enough corner ...quote]

I take it you mean radius on the points? A chamfer is the bevel on the edge of a part, and calling out a bevel to .050 will add a lot of additional cost.

Quite a few of the parts I work on state exactly what Steve said, "NOTE: PART TO BE FREE OF BURRS AND SHARP EDGES. " Depending on what services they have, tumbling might be a good option.

Jamie

The nice thing about such generic notes is that it gives the shop the freedom to do the job the best way they see fit, which usually saves you money.

Whenever you provide specifications for the manufacture of an item, you should always, as a designer, refrain from specifying how the part is to be made, unless, of course, it is critical.

For example, if you need a tapped 1/4-20 hole 1/2" deep, this is usually first drilled with a .201 diameter drill bit to a depth 3 threads deeper than the required tapped hole.

However, in point of fact, you do not care how the machinist puts in the tapped hole. He could do it with a particle beam for all you care. So in general, you should not tell the machinist how to drill and tap the hole - just specify what you want to achieve and leave it to the machinist.

Steve

To give you guys a little more detail ...

This job would be submitted on-line via an 'Auto-CAD lite' program. All specs and no comments (okay, there is a comment box you can add, but I agree that I should hand them a design, not a method).

The cheap machine for the job is a 'turret punch.' The turret punch can finish corners by 'chamfer.' I think they mean slicing the 90deg corner into two 45deg corners. That's what shows on the diagram at any rate when I select 'chamfering'. Chamfered corners only adds 1c per piece.

Rounded corners are an option if I select laser cutting. I noticed that for larger pieces there was little difference in cost between laser cutting and turret punching - but for these small pieces, prices jumped by 50%.

I appreciate the advice I have received so far. If anyone has any special knowledge of turret punch machines and small parts, I would be glad to hear of it. Is a 'turret punch' what you guys are refering to by 'CNC'?

Doh! I just found a description of this machine. "CNC Turret punching results in edges with a slight rounding on the top side and a slight burr on the bottom side." How slight, I wonder?

OK once upon a time I worked for a company briefly that produced specialty cabinets for electronics. Most of their work was done by CNC turret punch. The company sucked otherwise I would have stayed and been using their machinery for an mini-armoring business.

A turret punch functions like a giant hydraulic version of a whitney hole punch. It changes through punches and dies to chose basic shapes and uses them to nibble away the outer profile to the desired shape. Certain punch shapes can even create louvered vent slots etc. As with all punches the top is slightly rounded over and the bottom shows a break away or tear out.

For large plates turret punches are economical because the ejected bits are not a meaningfull precentage of the raw material. For plates the size of a dime you will likely consume material the size of a quarter. This may not be particularly relavent.

Counter sunk holes are easy. The first punch knocks in a hole. It is followed by a second punch at either 90 degrees or 120 degrees or whatever which 'smushes' the steel or aluminum into a chamfer. The original hole is occasionally oversized if the type of chamfering would cause close in. I do not know how they would chamfer long straight edges and I don't know any way to chamfer the back side.

The above comments about kerfs and tumbling are definetly correct. I tend to think of kerf data from a programing background and tumbling as a possible criteria by which to sort valid suppliers. You need neither if all you are doing is specifing the finished product. You could even finish off the print with:

No burrs or sharp edges.
Powder coat per ASTM ???? color spec ???.
All dimensions after coating.

and let the machine shop oversize the holes slightly to compinsate for the powder build up with you getting a beutiful black or maroon glossy plate.

Have fun.
Sean

Ron Broberg wrote:The cheap machine for the job is a 'turret punch.' The turret punch can finish corners by 'chamfer.' I think they mean slicing the 90deg corner into two 45deg corners. That's what shows on the diagram at any rate when I select 'chamfering'. Chamfered corners only adds 1c per piece.

I appreciate the advice I have received so far. If anyone has any special knowledge of turret punch machines and small parts, I would be glad to hear of it. Is a 'turret punch' what you guys are refering to by 'CNC'?

... slight burr on the bottom side.[/i]" How slight, I wonder?

I don't have the parts here, but slight can mean no more than a few thousands of an inch. I can measure if when I get a chance if you like. Not enough to be real hassle, that's kinda what I had in mind to have tumbling take care of it.

I haven't worked very much at all with lasered parts or with waterjet, but I do know about stamping. It wouldn't be hard to build dies for the parts you're describing. For such a small run, if I were doing it, I'd make a low grade die to punch the pieces out. They would be whatever shape needed. A radius on the corner would be pretty easy. Holes wouldn't be a problem.

A pincher press (also called a bleeder press) would make short work of something like this. 1280 parts is a pretty short run in terms of stamping parts. Most dies are made with thousands if not millions of parts in mind before maintenance.

For pieces like this, and for other lamellar plates, I've wondered if it would be worthwhile for me to make dies to stamp these parts. Right now I have limited access to a punch, but continuous access to make the dies.

I don't know how the online quote is setup, but leave the tolerance open. For instance, if I was handed a print that said that the pieces had to be .2500 +- .0002, it's gonna take more time than if it said .25 +-.03. For your use, I can't imagine that a real high tolerance would be needed.

Out of curiousity, how big are the holes in the hex pieces? Any holes in the rectangular pieces?

Jamie

Right now, it looks something like this:

Kikkou (1mm mild steel):
.651" point-to-point
.607" side-to-side
4x .118" holes (7.5/64 or 3mm)
Corners chamferred 0.05"
This is about the same size as a dime.
How far apart should the holes be set?

Haidate-Iyozane (1mm mild steel):
1.5"x2.0"
10x .118 diameter (3mm) (5 on each side (left and right)(one edge = 2 on top, 1 in middle, 2 on bottom))
Corners chamferred 0.05"
How far back from the edge should the holes be set?

Some examples from AJ Bryants site:
http://www.sengokudaimyo.com/katchu
http://www.sengokudaimyo.com/katchu/gra ... kawara.PDF
http://www.sengokudaimyo.com/katchu/gra ... /kikko.PDF

I did find finishing options on my spec program which included tumbling and powder finishes. Even tumbling added 30% to the pieces. Priced as a set (which is cheaper), one plain rectangular scale and one plain hexagonal button run about 50c - finished with tumbling, about 68c - cut by laser, about 72c. I might end up splitting the order anyway because powder coated scales could be mighty nice to have.

Kikko (the hexagons) are laced/sewn into fabric and are never seen. But the edges cannot be so rough as to damage the fabric its sewn into.

And to be clear ... I don't need chamfered holes. I just need to understand what a chamfered corner is.

I am pretty close to breaking even with a set of dies. If I double the number of pieces, it would be worth going for the die - but I think that's just too many pieces for the Japanese 'market.' This isn't really a money making venture but I don't want to sink a boat load of dough into it either.

If you like, I could send you the AutoCAD export.

Those pictures tell me exactly what I was curious about. They wouldn't be difficult dies to construct (especially in comparison to some). How crucial is the hole size? They should be able to make it quicker (and therefore a little cheaper) if you make the holes .125". It's a standard punch size.

Out of curiousity, if you have them construct this die, and want more, would they charge you all over again or use the die? You might be able to purchase the die outright and send it to them to stamp when needed. There are places that do nothing but that.

Not to step on any toes, but how much interest is there from how many people for pieces like this? I've considered making dies for schtuff like that....

Jamie

There is more information in this thread (a different board)
http://tousando.proboards18.com/index.c ... 1107067739

If you can beat their price, I would be happy to purchase from you. I'm just trying to fill a niche and not really trying to make money off this.

I have not actually contacted them about what happens with the die after the first order. I would need to order about 10000 kikkou for the die to pay for itself - that's roughly 10x what I think I need now.

Hey Jamie, how much would it cost to make dies that would make lamellar plates like in T Bob's essay?

Animal wrote:Hey Jamie, how much would it cost to make dies that would make lamellar plates like in T Bob's essay?

Ok, after losing a long post describing a lot of schtuff, I'll summarize.

Cost depends on how many pieces you hope to run with the die. Low grade and high grade dies can be made. $1000 or more would not be unheard of for a low grade die. It all depends on whether you want 10000 pieces or millions. Depending on the operations needed to make the die and the complexity of parts, you could get MUCH more expensive than that.

Different materials, thicknesses of materials, and overall shape of materials determines the press capacity required to punch the parts. Mild steel, aluminum, stainless or titanium all have different needs. Some places will use dies made elsewhere and run them. Otherwise, a suitable punch needs to accessible.

I can't give an exact number to answer your question, because of the variables. But having a die made isn't cheap. The presses aren't cheap. The material, in comparison, is cheap.

Jamie

Is there a way to simply rent time on a vertical mill? The punch would be very simple (the die, on the other hand . . .) and could be made fairly quickly. Then send it out for heat treating. Given the tools, I could do it, but that's several grand worth of tools that I don't have.

Thanks Jamie. I was just curious. We get ours plasma cut or some such but I was curious to know what dies would run.
I appreciate you taking the time.

Mate Precision Tooling is a large tooling company. Hex is one of the tooling shapes that they make. Every punch is custom made to your application and punch press. If you know someone with a punch press you could buy the tool yourself and let them use it for your order. Tooling should be around $500 for a small simple tool.
www.mate.com

You can also check out http://www.mfgquote.com/index.cfm. You can place a part drawing on the site and get bids from companies all over the country for any type of machining you could ever want.

I am a mechanical designer and do 3D cad work all the time. If anyone needs cad models or drawings let me know and I will try to help you out. I can output .iges, .dxf, .step and .prt (Unigraphics)

Giovanni

A cheaper alternative for smaller pieces like scales could be a fly press. Relatively cheap and dead simple to use.

farslayer wrote:
You can also check out http://www.mfgquote.com/index.cfm. You can place a part drawing on the site and get bids from companies all over the country for any type of machining you could ever want.


Giovanni

hahhahaahaha My brother is one of thier head nerds. He is the one in the back with the blond hair! here-http://www.mfgquote.com/partners_techPartners.cfm

I have thought of a fly/screw press, but haven't looked into it yet.

Making a die isn't a problem, I'm a machinist. The smaller one wouldn't be that hard to do. I keep debating with myself if I want to get into making armour dies. The larger lamellar plates really wouldn't be difficult either. I modeled one today just for kicks. I have the tools, materials, and abilities to make everything for the dies. I have limited access to a punch press which would be perfect for this. It's for a limited time, so I'm not sure I want to start making it, no longer have access, run out of pieces and then not be able to easily make more when needed.

If somebody out there has a punch press, I'd like to speak with them privately to see if we could work out a good deal.

In part of the post I lost from earlier, I had said that I could probably make a low grade, low run (~100,000 under ideal conditions) die for roughly $500.

Farslayer, what program(s) do you use for your modeling?

Jamie

I've always wondered if a moderatly skilled machinist couldn't convert a hydraulic log splitter into a press for shaping simple cops in a single press. I suppose it begs the question: could it form the basis for an albeit slow but powerful single stroke punch press?

Sean

Jamie

I use Unigraphics CAD, for my the work I do now. I have almost 2 years expeirence on SDRC and a little experience using Mechanical desktop.

Giovanni

Sean Powell wrote:I've always wondered if a moderatly skilled machinist couldn't convert a hydraulic log splitter into a press for shaping simple cops in a single press. I suppose it begs the question: could it form the basis for an albeit slow but powerful single stroke punch press?

Sean

Most hydraulic punch presses are a lot quicker. Log splitters don't always have the power either. I will be building myself a press for my bladesmithing, and I have thought about building an extra one for punching.

Jamie